Certain abbreviations that may be found in the description and/or in the Figures are herewith defined as follows:    3GPP Third Generation Partnership Project    ACK acknowledgment    AMC adaptive modulation and coding    BER bit error rate    BPSK binary phase shift keying    BW bandwidth    CAZAC constant-amplitude zero auto-correlation    CDM code division multiplexing    CM cubic metric    CP cyclic prefix    CQI channel quality indicator    DFT-S-OFDMA discrete Fourier transform spread OFDM (SC-FDMA based on frequency domain processing)    E-UTRAN evolved UTRAN    FBI feedback information    FDM frequency division multiplexing    FDMA frequency division multiple access    FFT fast Fourier transform    HARQ hybrid automatic repeat request    IFDMA interleaved FDMA    IFFT inverse FFT    L1 Layer 1 (physical layer)    L2 Layer 2 (data link layer)    LB long block    LTE long term evolution    MCS modulation coding scheme    NACK negative ACK    Node-B Base Station    eNB EUTRAN Node B    OBO output backoff    OFDM Orthogonal Frequency Domain Multiplex    PAPR/PAR peak to average power ratio    PRB physical resource block    PSK phase shift keying    PUCCH physical uplink control channel    QAM quadrature amplitude modulation    QPSK quadrature phase shift keying    QoS quality of service    SB short block    SC-FDMA single carrier, frequency division multiple access    SF spreading factor    SINR signal-to-interference and noise ratio    TPC transmission power control    TTI transmission time interval    UE user equipment    UL uplink    UTRAN universal terrestrial radio access network    ZAC zero autocorrelation sequence
A proposed communication system known as evolved UTRAN (E-UTRAN, also referred to as UTRAN-LTE) is currently under discussion within the 3GPP. The current working assumption is that the DL access technique will be OFDM, and the UL technique will be SC-FDMA.
Control channel multiplexing is performed in the UTRAN-LTE system, including control channel multiplexing in the SC-FDMA based UL. There are two different type of control signals to be carried in the UL:
1. Data associated control signaling including transport format and HARQ information. This information is associated with UL data transmissions.
2. Data-non-associated control signaling, such as CQI and/or ACK/NACK due to downlink transmissions.
Of particular interest to this discussion is the data-non-associated control signaling, the transmission of which may be divided into two separate classes:
a) data-non-associated control signaling multiplexed with UL data; and
b) data-non-associated control transmitted without UL data.
Reference in this regard may be had to 3GPP TR 25.814, v7.0, Section, 9.1.1.2.3, Multiplexing of L1/L2 control signaling, where it is stated that there are three multiplexing combinations for the uplinkpilot, data, and L1/L2 control signaling within a sub-frame that are considered for a single UE:
multiplexing of pilot, data, and data-associated L1/L2 control signaling;
multiplexing of pilot, data, and data-associated and data-non-associated L1/L2 control signaling; and
multiplexing of pilot and data-non-associated L1/L2 control signaling.
In single-carrier FDMA radio access, time-domain multiplexing is used for the above-mentioned three multiplexing combinations in order to retain the advantageous single-carrier feature with a low PAPR.
Both data-associated and data-non-associated control signaling are time-multiplexed with data and pilot within the sub-frame. Furthermore, the data-associated and data-non-associated control signaling from multiple UEs are multiplexed in the frequency or/and code domains associated with multiple pilot channels.
The data-non-associated control signaling can also be time-multiplexed with data if the UE has UL data transmission. Meanwhile, the data-non-associated control signaling, that transmits only the L1/L2 control, is multiplexed exclusively in a semi-statically assigned time-frequency region. This uplink control signaling is transmitted on a channel that can be referred to as a Physical Uplink Control Channel (PUCCH) in LTE terminology. The data-non-associated control signaling of different UEs is multiplexed using the frequency/time/code domain or a hybrid of them within the assigned time-frequency region. The exclusive time-frequency region can be separated into multiple separate frequency-time resources. The possibility for multiplexing of data-non-associated control signaling with data channel by exclusive frequency resource, i.e., frequency-multiplexing, is for further study.
FIG. 1 herein reproduces a part of FIG. 9.1.1.23-2 of 3GPP TR25.814, “Multiplexing scheme for L1/L2 control signaling, data, and pilot”, and assumes that data-non-associated control signaling for UEs that transmit only the L1/L2 control, is multiplexed exclusively in a semi-statically assigned time-frequency region (denoted with the asterisk in FIG. 1). On the contrary, UEs which have both UL data and data-non-associated control signaling utilize time-multiplexing between control and data.
It is important to note that data-non-associated control signaling transmitted in the UL presents special requirements for system design. In general, the transmitted information includes only a few information bits having tight delay requirements, and the ability to use re-transmissions is severely curtailed. Furthermore, the QoS requirement is stringent, e.g., for ACK/NACK signaling an error probability of the order of 10−2 or less is required. This indicates that frequency diversity is of high importance. In addition, maintaining the intra-cell orthogonality and low PAR properties of the SC-FDMA system should also be considered in the system design. Providing an optimized coverage area is also of importance.
Several contributions on data-non-associated channel multiplexing have been proposed thus far during the 3GPP standardization process for UTRAN-LTE.
For example, in R1-061862, “Uplink Non-data-associated Control Signaling”: Ericsson, Jun. 27-30, 2006, it is proposed to have a new sub-frame format with an additional short block for data-non-associated control signaling. At least one perceived problem with this proposal, however, is that the scalability of the resource is less than optimum.
Also by example, in R1-062065, “L1/L2 UL Control Mapping and Numerology”: Motorola, Aug. 28-Sep. 1, 2006, it is proposed to have a FDM-type of multiplexing combined with frequency hopping within a sub-frame. At least one perceived problem with this proposal is that the number of active sub-carriers is only two, which can lead to very high power differences between UEs occupying a large bandwidth. Thus, there is an increased probability that intra-cell orthogonality would be lost at least to some extent under practical transmission conditions, such as those where frequency and timing errors exist.
Additional related contributions include:    R1-061674, “Multiplexing Method of Uplink L1/L2 Control Channel”, NTT DoCoMo;    R1-061675, “Data-non-associated L1/L2 Control Channel Structure for E-UTRA Uplink”, NTT DoCoMo;    R1-061699, “Uplink ACK/NACK Signalling: FDM vs TDM”, Samsung;    R1-061779, “Multiplexing of control signalling in E-UTRA”, LG;    R1-061802, “Multiplexing and Link analysis of UL control channels”, Qualcomm, respectively; and    3GPP TR 25.814, section 9.1.1 incorporated by reference.
These various proposals suggest the use of the same DFT-S-OFDMA modulation scheme for both data-non-associated control signaling and for data. However, a problem that arises is that DFT-S-OFDMA is not the most optimum modulation option for the intended purpose.